In the production of polyurethane products, particularly soft polyurethane foams, stable dispersions of polyureas and/or polyhydrazodicarbonamides in polyethers (so-called "PHD-polyols") have achieved worldwide importance as starting products. Complete foam seats in the automotive industry are produced from PHD-polyols, particularly in the United States of America. By using PHD-polyols, an increased foaming reliability and a more favorable hardness/bulk density ratio of the cold-form foaming qualities is achieved. According to German Pat. No. 2,513,815 (corresponding in part to U.S. Pat. No. 4,089,835), such dispersions are continuously produced, such that the reaction of organic polyisocyanates with primary and/or secondary amino group-containing polyamines and/or hydrazines and/or hydrazides in relatively high molecular weight polyols takes place in a throughflow mixer. In order to achieve the lowest possible viscosity, an equivalent ratio (NCO/NH ratio) of from 0.8:1 to 1.05:1 is maintained.